class_docstr: Base Data Geneartor
code: def __getitem__(self, idx):
      if isinstance(idx, collections.Iterable):
          return [self[bidx] for bidx in idx]
      else:
          return self.line_examples[idx]
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  from __future__ import absolute_import
  import os
  import sys
  import six
  from io import open
  from collections import namedtuple
  import numpy
  import tqdm
  import paddle
  from pgl.utils import mp_reader
  import collections
  import time
  from pgl.utils.logger import log
  import traceback
label_desc: Use image node_id 5 for calling the BaseDataGenerator obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: unknown, self